JAVA 不兼容类型：对象无法转换为我的类型
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JAVA incompatible types: Object cannot be converted to my type
提问by macourtney7
I'm trying to make changes to my GUI in JavaFX by doing the work on a separate thread and returning the object required. However, after doing the work and task.setOnSucceeded() is triggered I attempt to retrieve the created object and get the error "incompatible types: Object cannot be converted to type VideoScrollPane".
我正在尝试通过在单独的线程上进行工作并返回所需的对象来更改 JavaFX 中的 GUI。但是，在完成工作并触发 task.setOnSucceeded() 后，我尝试检索创建的对象并收到错误“类型不兼容：对象无法转换为 VideoScrollPane 类型”。
I think this has something to do with raw types as it's within the listener this is happening but after looking around I couldn't find the suggestions I was looking for.
我认为这与原始类型有关，因为它在侦听器中正在发生，但环顾四周后，我找不到我正在寻找的建议。
Any light that can be shed would be much appreciated.
任何可以发出的光都将不胜感激。
Task task = new Task<VideoScrollPane>() {
VideoScrollPane vsp;
@Override protected VideoScrollPane call() {
try {
System.out.print("thread...");
ExecutorService executor = Executors.newCachedThreadPool();
Future<VideoScrollPane> future = executor.submit(new Callable<VideoScrollPane>() {
@Override public VideoScrollPane call() {
return new VideoScrollPane(mediaview, vboxCentre, username, project);
}
});
vsp = future.get();
} catch(Exception exception) { System.out.println(exception.getMessage()); }
return vsp;
}
};
new Thread(task).start();
task.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
@Override public void handle(WorkerStateEvent t) {
System.out.println("complete");
try {
//where the problem occurs
VideoScrollPane v = task.get();
} catch(Exception exception) { System.out.println(exception.getMessage()); }
}
});
采纳答案by Minty Fresh
This is because the task.get()is returning a value of type Object, but you're trying to assign it to v, which is a VideoScrollPane. You can prevent the error by doing a cast, like so
这是因为task.get()正在返回一个类型的值Object，但您试图将它分配给 v，这是一个VideoScrollPane。您可以通过执行强制转换来防止错误，就像这样
VideoScrollPane v = (VideoScrollPane)task.get();
Be warned, if task.get()returns something that isn't a VideoScrollPane, you'll get a ClassCastException.
请注意，如果task.get()返回不是 a 的内容VideoScrollPane，您将得到一个ClassCastException.
If you want to prevent the problem entirely however, consider fixing the declaration of task, by including a type for the generic parameter. You could change it to,
但是，如果您想完全避免该问题，请考虑task通过包含泛型参数的类型来修复 , 的声明。你可以把它改成，
Task<VideoScrollPane> task = new Task<VideoScrollPane>() {
This way, task.get()will now return a VideoScollPane, and you won't need a cast.
这样，task.get()现在将返回 a VideoScollPane，您将不需要演员表。
回答by Crazyjavahacking
The return type of your task.get();is Objectand not VideoScrollPane, change it to:
您的返回类型task.get();是Object和不是VideoScrollPane，将其更改为：
VideoScrollPane v = (VideoScrollPane) task.get();
回答by James_D
You have declared your Taskincorrectly. You need
你的声明是Task错误的。你需要
Task<VideoScrollPane> task = new Task<VideoScrollPane>() { ... }
